The U.S. Department of Energy faces one of the largest environmental challenges in the world. The Department's Environmental Restoration and Waste Management program has responsibility for identifying and reducing risks and managing waste at 137 sites in 34 states and territories where nuclear energy or weapons research and product resulted in radioactive and hazardous waste contamination.
Tests to quantify radionuclide contamination of soil, sediments, and groundwater will need to precede the remediation activities. Monitoring activities will continue even after completion of remediation activities. The number of radiochemical analyses being performed per year in the United States exceeds one million samples per year.
Radiochemical analyses involve specific isotopes or groups of isotopes. Tests are performed to determine quantities of radioisotopes of uranium, plutonium, cesium, radium, strontium, americium, iodine and a number of less frequently analyzed elements.
Radioactive strontium (isotopes Sr.sup.89 and Sr.sup.90) is one of the more frequent radionuclide contaminants found in groundwater or soils and sediments. Procedures for the analysis of strontium isotopes are documented in "DOE Methods for Evaluating Environmental and Waste Management Samples," U.S. Department of Energy, RP-500, March, 1993.
A common feature of all current radiochemical analyses is the labor-intensive nature of the tests, requiring the involvement of highly trained technicians. In the case of the analysis of radioactive strontium, the procedure involves one of several pre-concentration methods, a method to isolate and purify the Sr-fraction, and detection methods. Strontium is chemically separated from other sample constituents using a strontium selective chemical precipitation method. Repeated preconcentration, precipitation and extraction chromatography steps contribute to preparation time of several hours per sample. The use of columns of Sr-Spec.TM. extraction chromatography resin, supplied by Eichrom Industries, Inc., Darien, Ill., has somewhat simplified the isolation and purification of the Sr-fraction without substantially reducing the time required for the total analysis.
A solid phase extraction disk for use in direct analysis by solid-state luminescence has been described by E. J. Poziomek, "Solid State Extraction and Solid-State Spectroscopy for Monitoring Water Pollution," (Analytical Letters, 24(10), 913-1921 (1991). The extraction disk of the reference involves C-18 modified silica particles in a Teflon.TM. matrix.
U.S. Pat. No. 3,967,932 describes a method of analyzing cation-containing liquids in which a solution is passed through filter paper comprising fibers having cation-exchange functional groups. The cation-loaded filter paper is analyzed directly by, e.g., X-ray fluorescence spectroscopy, or the cation is eluted from the filter paper for subsequent analysis. Selectivity for specific cations is not described.
U.S. Pat. Nos. 4,142,020, 4,460,474, and 4,943,375, 5,344,624, and others, relate to the selective removal of ions including, e.g., strontium, uranium, plutonium, cesium, or yttrium, from aqueous solutions containing other ions by means of solid phase extraction columns comprising crown ether derivatives coated on solid supporting media, or by means of liquid-liquid extraction using crown ether derivatives.